Do You Have Ice Dams and Ice Back-Up? We Can Help!!!

Ice Dams and Back-Ups

An ice dam is a ridge of ice that forms at the edge of a roof and prevents melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas. Figure 1 shows a cross section of a home with an ice dam.

Figure 1

What Causes Ice Dams?

There is a complex interaction among the amount of heat loss from a house, snow cover, and outside temperatures that leads to ice dam formation. For ice dams to form there must be snow on the roof, and, at the same time, higher portions of the roof’s outside surface must be above 32˚F. For a portion of the roof to be below 32˚F, outside temperatures must also be below 32˚F. When we say temperatures above or below 32˚F, we are talking about average temperature over sustained periods of time.

The snow on a roof surface that is above 32˚F will melt. As water flows down the roof, it reaches the portion of the roof that is below 32˚F and freezes. Voila!–an ice dam.

Figure 2

The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that are on the average below 32˚F. So the water above backs up behind the ice dam and remains a liquid. The water finds cracks and openings in the exterior roof covering and flows into the attic space. From the attic it could flow in the exterior walls or through the ceiling insulation and stain the ceiling finish.

Preventing and Dealing with Ice Dams

Ice dams can be prevented by controlling the heat loss from the home.

Immediate Action:

• Remove snow from the roof. This eliminates one of the ingredients necessary for the formation of an ice dam. A “roof rake” and push broom can be used to remove snow, but may damage the roofing materials.
• In an emergency situation where water is flowing into the house structure, making channels through the ice dam allows the water behind the dam to drain off the roof. Hosing with tap water on a warm day will do this job. Work upward from the lower edge of the dam. The channel will become ineffective within days and is only a temporary solution to ice dam damage.

Long Term Action:

• First, make the ceiling air tight so no warm, moist air can flow from the house into the attic space.
• After sealing air leakage paths between the house and attic space, consider increasing the ceiling/roof insulation to cut down on the heat loss by conduction.
• Both of these actions will increase the snow load that your roof has to carry because it will no longer melt. Can your roof carry the additional load? If it is to current codes, there should not be a structural problem. Roofs, like the rest of the home, should have been designed to withstand expected snow loads.

Article excerpts courtesy of the University of Minnesota.

For more information regarding ice dams and back-ups, please call us at 1-866-STAYDRY.